Today's electric vehicles are widely used in the Thyristor chopper speed regulation, through the change of the motor's end voltage, control the current of the motor, to achieve the motor stepless speed regulation. In the continuous development of electronic power technology, it is also gradually replaced by other power transistors (GTO, MOSFET, BTR and IGBT) chopper speed-regulating devices. From the development of technology, with the application of new type drive motor, the change of speed control of electric vehicle to the application of DC inverter technology will become an inevitable trend.